JPS61253655A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording film with an enhanced photomagnetic effect by incorporating a crystalline part having 10-500Angstrom grain diameter into the amorphous rare earth metal-transition metal alloy in an amorphous alloy film. CONSTITUTION:A vessel 1 communicates with a vacuum evacuation system 5 and a gaseous Ar introducing system 6. An RF electric power source 7 for supplying high-frequency electric power between a substrate 3 and a target 4 and a DC electric power source 8 for impressing a negative bias voltage to the substrate 3 are connected in series between an anode and a cathode. An amorphous alloy film in the optical recording medium is formed by a high- frequency sputtering device. The amorphous alloy film is directly formed on a discoid and grooved acrylic substrate as the substrate 1 having 200mm diameter. Then a protective film of Si3N4, etc., is immediately formed on the formed amorphous alloy film while keeping the vacuum conditions. By such film formation, a photomagnetic recording medium contg. a crystallite part having 50-500Angstrom grain diameter in the amorphous structure of the amorphous alloy film is obtained. Besides, the alloy film consists of a rare earth metal-transition metal alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an E-DRAW type optical disk, and more particularly to a magneto-optical recording medium having an optical recording film mainly made of rare earth metals and transition metals.

BACKGROUND ART Conventionally, alloys of rare earth metals and transition metals have been created under certain conditions using methods such as high frequency sputtering.
It is known to have an amorphous structure and to have uniaxial magnetic anisotropy perpendicular to the film surface.

This property can be utilized as a recording film for magneto-optical recording media.

That is, recording and reading of information is performed as follows. First, a laser beam is focused on an amorphous alloy film having -axis magnetic anisotropy, and the focused portion is locally heated to around the Curie temperature or compensation temperature. Due to the thermal effect of thermal demagnetization or magnetization reversal in the focused part at this time,
Reversal magnetic domains can be formed within the plane of the alloy film that is uniformly magnetized in one direction. Next, a polarized laser beam is incident on the formed reversed magnetic domain, and the presence or absence of a reversed magnetic domain is detected as a signal from the rotation of the principal axis of the polarization ellipsoid due to the Faraday effect or Kerr effect in the reflected light and the change in ellipticity. . In this way, the presence or absence of reversed magnetic domains in the recording medium can be determined.
1'' and 110'', records can be read.

Conventional amorphous alloys of rare earth metals and transition metals, such as Gd'rbFe (gadolinium-terbium-iron) and TbFeCo (terbium-iron-cobalt), have excellent magneto-optical effects and magnetic properties, especially the Curie point, low compensation temperature, and Since it has a coercive force and is suitable as a magneto-optical recording material, it is attracting attention as a recording film material for magneto-optical recording media and is being put into practical use.

However, when these amorphous alloys have a completely amorphous structure, the magnetic anisotropy constant KLJ
is small, and the Kerr rotation angle θk is not sufficient, so the figure of merit rπ×0k (R is reflectance) cannot be obtained large. A magneto-optical recording medium using such an optical recording film having a completely amorphous structure has not yet achieved a practically necessary C/N ratio. Furthermore, in magneto-optical recording media using an optical recording film with an amorphous structure, material deterioration such as oxidation occurs, resulting in problems in long-term reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording medium that exhibits little change over time and has excellent long-term storage stability.

The magneto-optical recording medium of the present invention comprises a substrate and an amorphous alloy film supported on the substrate, which is mainly made of a rare earth metal-transition metal and has uniaxial magnetic anisotropy in a direction perpendicular to the film surface. The magneto-optical recording medium is a magneto-optical recording medium which has a magneto-optical effect enhanced by including a microcrystalline portion with a grain size of 10 to 500 in the amorphous state of a rare earth metal-transition metal alloy. It is characterized by

Embodiment Hereinafter, an embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 is a schematic sectional view showing a high frequency sputtering apparatus for carrying out the present invention. A plurality of plastic or ceramic substrates 3 attached to a cathode and rotatable substrate holder 2 are rotatably arranged in the upper part of the container 1 of the device, and targets 4 (single targets, composite targets, alloy targets) are arranged as anodes in the lower part of the container 1. any target) is placed.

The container 1 communicates with a vacuum exhaust system 5 and an Ar gas introduction system 6. Radio frequency (RF) II is connected between the substrate 3 and the target 4.
An RFm source 7 for supplying power and a DC power supply 8 for applying a negative bias voltage to the substrate 3 are connected in series between the anode and cathode. The surroundings of Targera 1 to 4 and the container 1 are grounded and shielded.

The amorphous alloy film in the optical recording medium of this example is formed using the high frequency sputtering apparatus under the following conditions.

RFffi power: 0.5~5.0KW DC voltage knee 50~-150V Ar pressure: Q, 5~3.5Pa Distance between substrates: 20~230mm Substrate rotation speed: 0~1100rp Sputtering speed: 50~1000 people/min Target: Composite target with Ni on Fe-C0 alloy 5'' target and T b 5'' target.
Nickel), 1) t (platinum), Pd (palladium>
, cr<chromium) 1MO (molybdenum), B (boron)
, Si (silicon), AU (aluminum), Ge (germanium), and (2) (vanadium).

Under the above conditions, an amorphous alloy film is directly formed on a disc-shaped grooved acrylic substrate with a diameter of 200 mm as the substrate 1,
Thereafter, a protective film such as 513N4 is immediately provided on the amorphous alloy film formed while maintaining the vacuum state. By forming the film in this manner, it is possible to obtain a magneto-optical recording medium containing microcrystalline portions with a grain size of 50 to 500 grains in the amorphous structure of the amorphous alloy film.

The graph in FIG. 2(a) shows an X-ray diffraction pattern obtained by X-ray analysis of an amorphous alloy film produced using a high-frequency sputtering device. The structure of the alloy film is analyzed based on the X-ray diffraction pattern waveform and the microcrystalline state determined by TEM. In the graph of FIG. 2(b), the horizontal axis represents the substrate bias voltage, and the vertical axis represents the Kerr rotation angle θk. As can be seen, an amorphous alloy film containing microcrystals can be produced at a substrate bias voltage of -50 to -150V. It is also seen that an amorphous alloy film having a large θk (Kerr rotation angle) can be obtained when the substrate bias voltage is around −100V.

Figure 3 shows the magneto-optical recording medium of this example produced in this manner and the one produced by the conventional method that does not contain any microcrystal grains at the same location at room temperature 20'C and humidity 50% R, H. 3 is a graph showing the deterioration of the C/N ratio over time when the data is repeatedly erased, recorded, and reproduced. The horizontal axis of the graph shows the passage of time, the vertical axis of the graph shows the C/N ratio, curve A shows the change over time of the magneto-optical recording medium of the present invention, and curve B
Figure 2 shows the change over time of a conventional magneto-optical recording medium. As can be seen, the magneto-optical recording medium of the present invention having an amorphous alloy film containing microcrystals has a higher C/N ratio and is less likely to deteriorate.

Further, the background noise due to the inclusion of microcrystalline portions in the amorphous alloy film which is the magneto-optical recording film of the magneto-optical recording medium of the present invention was almost negligible. Further, after 10,000 hours, almost no growth of microcrystals with a grain size of 500 Å or more in the amorphous alloy film containing microcrystals was observed.

In the above embodiment, an example was shown in which the film was manufactured using a high-frequency sputtering device, but an amorphous alloy film partially containing a microcrystalline structure can also be formed by methods such as ion blasting, ion beam sputtering, and MBE. Also,
An additional protective layer may be provided between the grooved substrate and the magneto-optical recording layer to increase the reliability of the magneto-optical recording medium.

Effects of the Invention As described above, according to the present invention, in an amorphous alloy film made of a rare earth metal-transition metal alloy, the grain size is
By including 500 microcrystals, it is possible to obtain a magneto-optical recording medium with a high C/N ratio and excellent long-term storage stability with little change over time.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a high-frequency sputtering apparatus for carrying out the present invention, and FIG. 2 is a graph showing changes in the Kerr rotation angle θ and substrate bias voltage of a magneto-optical recording medium according to the present invention. FIG. 3 is a graph showing the C/N ratio deterioration characteristics of a conventional optical recording medium and an optical recording medium according to the present invention. Explanation of symbols of main parts 1... Container 2... Cathode and rotatable substrate holder 3...
・Substrate 4... Target (single target, composite target, or alloy target may be used) 5... Vacuum exhaust system 6... Ar gas introduction system 7... ...RF power supply 8...DC power supply

Claims (2)

[Claims] (1) A magneto-optical recording medium comprising a substrate and an amorphous alloy film supported on the substrate, the main material being a rare earth metal-transition metal and having uniaxial magnetic anisotropy in a direction perpendicular to the film surface, A magneto-optical recording medium characterized in that at least a part of the amorphous alloy film is microcrystalline with a grain size of 10 to 500 Å. (2) The amorphous alloy film is a multi-component alloy film whose general formula is (R_xT_1_-_x)_1_-_yS_y using x and y as atomic ratios, where R is one type selected from Gd, Tb, and Dy. These are the above rare earth metals, T is one or more transition metals selected from Fe and Co, and S is Ni and Pt.
, Pd, Cr, Mo, B, Si, Al, Ge, and one or more metals selected from V, and x and y are 0.1
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is made of an alloy having a value in each of the ranges of ≦x≦0.4 and 0.005≦y≦0.4.